Process and apparatus for drying wood

Abstract

Drying stacked cut wood in a drying chamber is accomplished by conducting air between the layers of cut wood. Before and/or during the drying, the air velocity profile in the plane of admission into the stack is adjusted to a modifiable theoretical value. The drying apparatus has at least two measuring sensors for the wood moisture level and/or the flow velocity of the air. The sensors are arranged at some distance from each other in the area of the stack. A flow control system is adjustable dependent upon the measured values obtained by the measuring sensors.

What is claimed is: 
     
       1. A process for drying cut wood arranged in a stack with a plane of admission in a drying chamber and with interposed stack strips, comprising the steps of: generating an air flow,   directing the air flow onto the plane of admission of the stack where channels formed between the cut wood layers begin,   directing the air flow in a sequence to produce a concentration of air flow at different parts of the plane of admission producing a higher velocity air flow in the channels beginning in a part of the plane of admission experiencing a concentrated air flow, than in the other channels,   measuring at least one of wood moisture, wood moisture gradient and flow velocity in the stack on different levels,   adjusting the concentration of air flow dependent upon measured values of at least one of wood moisture, wood moisture gradient and flow velocity so that the flow velocity in the channels with the higher velocity avoids moisture equalization of air and wood within such channels, and   changing the concentration of air flow to a next part of the plane of admission after a period dependent upon measured values at least of one of wood moisture gradient and wood moisture.   
     
     
       2. A process according to claim 1 wherein the air flow is generated by at least one fan. 
     
     
       3. A process according to claim 2 wherein the concentrate of air flow is adjusted by varying the direction of the fan. 
     
     
       4. A process according to claim 2 wherein the concentrate of air flow direction is adjusted by varying air flow control means in the drying chamber. 
     
     
       5. A process according to claim 2 wherein adjustment of the concentrate air flow is modified in response measurements of wood moisture made of at least two moisture measuring points spaced from each other in the stack. 
     
     
       6. A process according to claim 5 wherein the measurements of wood moisture determine a moisture gradient in the wood. 
     
     
       7. A process according to claim 5 wherein air flow velocity is evaluated at at least one point directly adjacent to one of the moisture measuring points. 
     
     
       8. A process according to claim 5 wherein durations of directing air flow against each part of the stack plane of admission are adjusted and set dependent on moisture measurements of the wood in the corresponding partial area. 
     
     
       9. An apparatus for drying cut wood arranged in a stack with a plane of admission and with interposed stack strips, comprising: a drying chamber;   at least one fan means for producing air flows mounted in said drying chamber;   at least two sensor means, mounted in said drying chamber, for measuring at least one of wood moisture, wood moisture gradients and air flow velocity at two measuring points spaced from each other in said drying chamber;   adjustable air flow regulating means for directing the air flows in the chamber onto the plane of admission of the stack where channels formed between the cut wood begin and for modifying the air flows to produce a concentration of air flow at different parts of the plane of admission producing a higher velocity air flow in the channels beginning in a part of the plane of admission experiencing a concentration of air flow, than in the other channels; and   control means, coupled to said sensor means and said regulating means, for adjusting said regulating means in sequence dependent on measurements obtained by said sensor means.   
     
     
       10. An apparatus according to claim 9 wherein said drying chamber comprises a wood receiving space and a flow passage separated from and adjacent to said wood receiving space; and said air flow regulating means comprises relatively adjustable air conducting surfaces positioned at opposite ends of said flow passage. 
     
     
       11. An apparatus according to claim 10 wherein said flow passage is located above said wood receiving space. 
     
     
       12. An apparatus according to claim 10 wherein said air deflecting surfaces comprise individually adjustable deflecting elements, and are located at different levels on air entry and air discharge sides of the stack of cut wood. 
     
     
       13. An apparatus according to claim 10 wherein adjustable mounting means supports said fan means in said flow passage for varying directions of said fan means. 
     
     
       14. An apparatus according to claim 10 wherein said air flow regulating means comprise air conducting surfaces pivotally mounted in said drying chamber. 
     
     
       15. An apparatus according to claim 9 wherein said air flow regulating means comprise air conducting surfaces supported by mounting means for permitting height adjustment of said air conducting surfaces in said drying chamber. 
     
     
       16. An apparatus according to claim 9 wherein said air flow regulating means comprise air conducting surfaces and setting motors for varying positions of said air conducting surfaces. 
     
     
       17. An apparatus according to claim 9 wherein setting motor means is coupled to said fan means to vary positioning thereof.